Tom Stemmle writes to say that the Dave who was functioning as substitute bandleader in that Tonight Show clip is Dave Grusin. Hey, I've heard of Dave Grusin. He's been the composer on an awful lot of great movies and has been nominated for (and occasionally won) a mess of Grammy awards and Oscars. A week or so ago, I re-watched one of my favorite films, And Justice For All, and it had a score by Dave Grusin. That's cool that that's him.
Meanwhile, Tim Dunleavy notes that the date given for that clip — 10/03/1965 — must be wrong because October 3 of that year was a Sunday. So your guess is as good as mine.
And that's about all I have time to post right now because I have a deadline that needs meeting and, heck, I've put up tons of content the last few days. I'm entitled to coast one day a week. Ergo, I have put up a photo of a soup can to indicate that posting will be light here the rest of the day…or however long it takes me to finish this script.